JPS5924383A - Optical information reader - Google Patents

Abstract

PURPOSE:To ensure accurate reading through a simple device even with the printing of a heat-sensitive printer, by using a light source of a diode which emits high-luminance red light having a wavelength within a range of 660+ or -60nm to read information recorded optically. CONSTITUTION:Plural diodes which emit the high-luminance red light having a wavelength within a range of 660+ or -60nm are arranged in a row. Then the information to be read is irradiated, and this reflected light is detected by a reading sensor diode. The light emitting diode has a spectrum distribution as shown by B in the figure, and a sensor diode has the sensitivity characteristics as shown by A in the figure. The reflection factor of black color has the characteristics as shown by C for a bar code printed by a heat-sensitive printer. Only the reflection factor approximate to 40% is detected for the black color printed by said heat-sensitive printer. This avoids incapability of reading, and furthermore an ordinary print can also be read with no problem as long as a contrast is higher than a normal level. As a result, an infrared filter can be excluded to miniaturize an optical information reader.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides barcodes printed on recording media such as labels,
The present invention relates to an optical information reading device that reads optical information such as characters.

Conventionally, this type of device uses a tungsten lamp to irradiate illumination light onto a label that records optical information such as barcodes and characters, and forms an information image based on the reflected light on the surface of a reading sensor (image sensor). The image is then converted into an electrical signal by the electronic scanning reading operation of the sensor.

Since the tungsten lamp used for this illumination emits illumination light with a large amount of infrared wavelength components, there is no problem when reading information printed with ordinary carbon-based black ink, but information printed with a thermal printer is not a problem. In this case, the light reflectance of the black background part becomes high in the infrared wavelength component, making it impossible to distinguish it from the white background part and making it impossible to read.

As a countermeasure, since the light sensitivity of ordinary semiconductor image sensors and other reading sensors is high in the infrared wavelength region, the light sensitivity of the infrared wavelength is compared to the sensitivity of the visible light region. In order to achieve low sensitivity, it was customary to provide an infrared cut filter that cuts out infrared wavelength components.

However, when this infrared cut filter is provided, its cut characteristics are sufficiently high in the infrared wavelength region, and are considerably low from the near infrared light to the visible light region; Since it does not reach zero in the light region, the luminance of the tungsten lamp must be increased to take into account the reduction due to the filtering effect, resulting in problems such as an increase in the size of the light source and an increase in the amount of heat generated by the light source.

The present invention has been developed in view of the above problems, and uses a normal reading sensor and eliminates the need for an infrared cut filter, making it possible to read optical information printed with normal ink as well as optical information printed by a thermal printer. It is intended to be.

To this end, in the present invention, a light emitting diode that emits red light with a wavelength in the range of 660±60 nm at high brightness is arranged as a light source of the illumination light irradiation means in an optical information reading device equipped with an electronic scanning type reading sensor. The configuration is set as follows.

The present invention will be described below with reference to embodiments shown in the drawings.

Figure 1 is a partially cutaway diagram of the configuration, and Figure 2 is an exploded explanatory diagram of the main parts.l is a high-intensity red light emitting diode used as a light source, and its emission spectrum is 660±60 nm.
The peak value is within the range of . 2 is a red light emitting diode of the same kind placed in parallel with the red light emitting diode 1, and the resistance value of the resistor connected in series with each light emitting diode is changed to make the illuminance slightly higher than that of the two outer light emitting diodes 1 and 2. I keep it low. A light scattering material 3 scatters the illumination light from the red light emitting diode 1.2 to make it uniform over a predetermined range. Reference numeral 4 denotes a recording medium, on which a barcode 5 of optical information is printed.

Reference numeral 6 denotes a flat reflecting mirror, which reflects the light reflected from the barcode label 4 and changes its direction. A lens 7 collects reflected light from the barcode label 4, passes through an aperture member 8, and forms a barcode image at a predetermined position. 9 is an image sensor as a reading sensor, which has a one-dimensional resolution of 1024 bits by arranging a large number of photo elements in a line, and has an emission spectrum of a red light emitting diode (1.2).
The peak region of spectral sensitivity is around 660±601). Reference numeral 10 denotes a hand-held case, which is connected to a data processing device via a signal cable for transmitting and receiving various electrical signals between the inside and outside of the case.

FIG. 3 shows a characteristic diagram, in which the spectral sensitivity characteristics of the image sensor 9 and the wavelength distribution characteristics B of the light emitting diode 1.2 are shown.
This represents the reflectance characteristic C of black (black bar) of the barcode label 4 printed by a thermal printer.

Here, the emission spectrum distribution of the light emitting diode 1.2 is 660±30 nm.

The peak value of the spectral sensitivity characteristic of the image sensor 9 is 700n
m is shown as an example, and according to the reflectance characteristics of the black bar of information printed by a thermal printer, the emission spectrum of the illumination light from the light source is 660.
It will be limited to a wavelength range of ±60 nm.

Next, the operation of the above configuration will be explained.

Now, place the hand-held reading device at the position shown in Fig. 1 on the tzH-code label 4 printed with a thermal printer, and turn on the four high-intensity red light emitting diodes 1.2. The red illumination light generated by this emission passes through the light scattering material 3 and is irradiated onto the barcode label 4. Due to this light irradiation, the reflectance differs according to the white bar and black bar on the barcode label 4. Light intensity distribution is barcode 5
A barcode image in a direction orthogonal to each bar is imaged onto a reading line along which photo elements of an image sensor 9 are lined up through an optical system including a lens 7 and an aperture member 8 corresponding to the bar code.

Therefore, the barcode image can be converted into an electrical signal by the electronic scanning reading operation by the electronic control circuit of the image sensor 9.

At this time, the image of the barcode 5 on the barcode label 4 is formed on the reading line of the image sensor 9 and the barcode 5
The optical path length between 1<- is longer than the reflected optical path length at both ends of the bar code than the reflected optical path length at the center of the code, but the luminous intensity of the outer red light emitting diode 1.1 Because the barcode image formed on the image sensor 9 has a uniform brightness over the entire area, the level of the electrical signal converted by the image sensor 9 is stabilized, and the barcode image formed on the image sensor 9 has a uniform brightness. This contributes to simplifying signal processing and increasing accuracy.

Furthermore, since the emission spectrum of the red light emitting diode 1.2 is around 660 nm, the reflection characteristics from the barcode 5 printed with a thermal printer are as shown in the characteristic diagram in Figure 3. In this case, the reflectance of the black bar of barcode 5 is approximately 80% to 90%, and can be distinguished from the white bar, which has a reflectance of approximately 100%.At this time, the reflectance of the black bar is approximately 80% to 90%. Although it is desirable that the wavelength be close to zero, it is limited to a wavelength range in which the sensitivity of the image sensor 9 is less degraded, and red light around 660 nm is the overall most suitable wavelength.

In other words, if we look at the reflectance of a black bar printed with a thermal printer, it is approximately 0.83 (P) at a wavelength of 900 nm.
CS (Printed Contrast 5tan
dard J value -0°02), approximately 0.0 at a wavelength of 660 nm.
53 (PC3 (M = 0°37), wavelength of 550 nm is about 0.08 (PC3 value = 0°89), the reflectance of the black bar is high at long wavelengths, and the reflection of the black bar is higher as the wavelength goes to visible light. The rate decreases, and the PC8 value increases.Therefore, it can be seen that shorter wavelengths are better, but when looking at the spectral sensitivity characteristics of the silicon-based semiconductor image sensor 9, the peak value is 650~ The spectral sensitivity of the image sensor 9 is approximately 8 at a wavelength of 600 nm.
It will be around 0% to 90%.

From the above, when looking at both the reflectance of the black bar printed with a thermal printer and the spectral sensitivity characteristics of the image sensor 9, it is clear that a light emitting diode with an emission spectrum within the range of 660±60 nm can be used as an optical information reader. It turns out that it is good to use it as a light source.

In addition, other normally printed labels can be read without any problem if the PCS value specified by the JIS standard is above the standard.

Furthermore, compared to the case where a tungsten lamp with a large amount of infrared wavelength components is used, the red light emitting diode 1.2 has no infrared wavelength components, so the infrared light peculiar to the silicon-based semiconductor photo element of the image sensor 9 is It is also possible to prevent problems such as non-uniformity of sensitivity caused by

In addition, since a high-brightness red light emitting diode 1.2 is used as the light source, the light source can be made smaller compared to the case where a tungsten lamp is used, and the amount of heat generated by the light emitting action is also reduced. It can be made very small, the life of the light source can be extended, and its maintenance can be simplified.

In the above embodiment, a plurality of round or square light emitting diodes are used as the red light emitting diodes 1.2, but the entire surface of the barcode 5 on the barcode label 4 can be illuminated. One surface-emitting high-intensity red light-emitting diode may be used.

In addition, although the example has been shown in which the light emitting illuminance of the two outer red light emitting diodes 1 and l and the two inner red light emitting diodes 2 and 2 are changed, the light emitting illuminance adjustment circuit is designed to equalize the light emitting illuminance of each light emitting diode. may be simplified.

Further, although a hand-held type reader is illustrated as an example, the present invention may be applied to a stationary type reader in which only the barcode label 4 is moved.

Moreover, although the barcode 5 is used as the optical information as an example, other codes, characters, etc. may be used as the optical information.

Further, although a linear one-dimensional image sensor is used as an example of the reading sensor, other sensors such as a planar two-dimensional image sensor may be used.

As described above, according to the present invention, a normal reading sensor is used, and an infrared cut filter is not required, and in addition to reading optical information printed with normal ink, it is also possible to easily read optical information printed by a thermal printer. It has the excellent effect of being able to read with high precision.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway configuration diagram showing one embodiment of the present invention, and FIG.
The figure is an exploded explanatory view of the main parts, and FIG. 3 is a characteristic diagram for explaining the operation. 1.2...Red light emitting diode serving as a light source of the irradiation means, 3...Light scattering material 94...Barcode label as a recording medium, 5...Barcode for optical information, 6...
・Plane reflecting mirror, 7... Lens, 8... Diaphragm member, 9
...Image sensor as a reading sensor. Representative Patent Attorney Takashi Okabe

Claims (1)

[Scope of Claims] Irradiation means for irradiating optically recorded information to be read with light, and imaging means for forming an information image at a predetermined reading position by light reflected from the information to be read by this light irradiation. An optical system, and a reading sensor arranged at this reading position and having photo elements arranged in a linear or planar manner for converting the information image imaged on the surface into an electrical signal by an electronic scanning type reading operation. An optical information reading device comprising: A light emitting diode that emits high-intensity red light with a wavelength in the range of 660±60 nm is disposed as a light source of the irradiation means.